JP6588596B2 - Adhesive layer and adhesive film - Google Patents

Description

  The present invention relates to an adhesive layer and an adhesive film used for bonding optical members such as polarizing plates. More specifically, the present invention has a low dielectric constant and dielectric loss value used for bonding optical members in the production of an ITO film-equipped liquid crystal panel called an on-cell panel. Provided are a pressure-sensitive adhesive layer and a pressure-sensitive adhesive layer and a pressure-sensitive adhesive film which have flexibility, rigidity, durability and reworkability.

  In recent years, various display devices having a capacitive touch panel externally attached to a liquid crystal panel, such as smartphones, tablet terminals, and tablet PCs, are widely used. In such a display device, a physical space exists between the liquid crystal panel and the touch panel. For this reason, external light etc. reflected on the upper surface of a liquid crystal panel or the lower surface of a touch panel, and there existed a problem that the visibility in bright environments, such as outdoors, fell.

  As a method for solving the problem that the visibility is lowered, an in-cell display device in which a function of a touch panel is incorporated in a liquid crystal pixel (see, for example, Patent Document 1) has been proposed. However, it has not been put into practical use because of a complicated manufacturing process and a decrease in product yield and technical difficulty in improving image display performance.

  On the other hand, recently, an on-cell display device (for example, see Patent Document 2) has been proposed. In the on-cell display device, a touch sensor including a transparent electrode pattern is formed between a color filter and a polarizing plate, and the function of the touch panel is formed between the color filter substrate and the polarizing plate. The on-cell method has an advantage that the yield of the product is less decreased. For this reason, the on-cell method is expected to develop in the future as a promising manufacturing technique for liquid crystal panels incorporating a touch panel.

  However, the capacitive touch panel is susceptible to noise because it is a sensor that senses changes in the electromagnetic field. Therefore, in order to prevent erroneous recognition of the contact position, it has been proposed to stack a low dielectric constant film in the laminated structure or to provide a low dielectric constant member on the wiring line of the capacitance sensor ( For example, see Patent Documents 3 to 5).

JP 2009-258182 A JP 2014-045001 A JP2013-082880A JP 2012-094017 A JP 2013-003758 A

By the way, although the adhesive concerning patent document 3 has the outstanding insulation whose relative dielectric constant is 3.5 or less, it is unknown whether it is an adhesive layer which has a softness | flexibility and rigidity.
In Patent Documents 4 and 5, in order to prevent erroneous recognition of a capacitive touch panel, a low dielectric constant film is laminated in the laminated structure, or a low dielectric constant is provided on a wiring line of a capacitive sensor. However, the method of manufacturing the low dielectric constant member to be used is not specifically shown.

As described above, in the prior art, it can be used for bonding optical members, and has a low dielectric constant, excellent insulation performance, flexibility, rigidity, durability, and reworkability. The film was not known.
There is a need for pressure-sensitive adhesive layers and pressure-sensitive films that can be used for bonding optical members, overcoming these requirements and problems in the prior art.

  The present invention is a pressure-sensitive adhesive layer having a low dielectric constant and dielectric loss compared to a conventional pressure-sensitive adhesive layer, and has a pressure-sensitive adhesive layer and a pressure-sensitive adhesive film that have flexibility, rigidity, durability, and reworkability. The issue is to provide.

  In order to solve the above problems, the pressure-sensitive adhesive layer of the present invention has butyl (meth) acrylate as an essential monomer as an acrylic polymer, does not use an aromatic-containing monomer, and contains a carboxyl group as a functional group-containing monomer. The technical idea is to use only a hydroxyl group-containing monomer without using a monomer, to use only an adduct of tolylene diisocyanate as a crosslinking agent, and to use a silane coupling agent in combination with the copolymer.

To solve the above problems, the present invention includes an acrylic polymer, a crosslinking agent, a pressure-sensitive adhesive layer formed by crosslinking a pressure-sensitive adhesive composition comprising a silane coupling agent, the acrylic polymer, (A ) alkyl (meth) acrylate monomers of the number of carbon atoms in the alkyl group is C1 to C14, and alicyclic-containing monomer, and at least one or more of the total of 100 parts by weight of the monomer group consisting of branched structure an alkyl group containing monomer, ( B) A copolymer obtained by copolymerizing 0.1 to 3.5 parts by weight of a hydroxyl group-containing copolymerizable vinyl monomer, and a total of 100 parts by weight of the above (A) comprises butyl (meth) acrylate. in a proportion of 30 to 60 parts by weight, (B) the hydroxyl group-containing copolymerizable vinyl monomer is 8-hydroxy-octyl (meth) acrylate, 6-hydroxyhexyl (meth) Acrylate, 4-hydroxybutyl (meth) acrylate, and a 2-hydroxyethyl (meth) acrylate, at least one or more selected from the group of compounds consisting of the acrylic polymer has an aromatic group-containing (meth) An acrylate monomer and a carboxyl group-containing copolymerizable vinyl monomer are not contained, the acid value of the acrylic polymer is 0.1 or less, and the total of 100 parts by weight of (A) is triglyceride as the crosslinking agent. Only from 0.01 to 1.5 parts by weight of an isocyanate compound that is a trimethylolpropane adduct of diisocyanate, and the silane coupling agent, from the group consisting of an epoxy group, a (meth) acryloxy group, a mercapto group, and an amino group Silane cup having at least one selected organic functional group The ring agent was contained at a ratio of 0.01 to 2.0 parts by weight, the gel fraction of the pressure-sensitive adhesive layer was 40 to 75%, and the pressure-sensitive adhesive layer was measured by laminating to a thickness of 1000 μm. dielectric constant at a frequency of 100kHz is 1.50 to 5.50, and dielectric loss to provide a pressure-sensitive adhesive layer, wherein the Ru der 0.01 to 0.09.

  The acrylic polymer does not contain an aromatic group-containing (meth) acrylate monomer and a carboxyl group-containing copolymerizable vinyl monomer, the acrylic polymer has an acid value of 0.1 or less, The pressure-sensitive adhesive containing 0.01 to 1.5 parts by weight of the isocyanate compound with respect to a total of 100 parts by weight of the monomer excluding the hydroxyl group-containing copolymerizable vinyl monomer and crosslinking the pressure-sensitive adhesive composition The layer has a weight average molecular weight of 300,000 to 2,000,000, and the adhesive layer is laminated to a thickness of 25 μm on one side of the substrate, and then the adhesive force after 23 ° C. × 10 days is 1.5 to 10 N / 25 mm. It is preferable that

  The pressure-sensitive adhesive composition preferably further contains 0.01 to 2.0 parts by weight of a silane coupling agent with respect to a total of 100 parts by weight of monomers excluding the hydroxyl group-containing copolymerizable vinyl monomer. .

  The cross-linking agent is an isocyanate compound and is preferably a trimethylolpropane adduct of tolylene diisocyanate.

  The compound group in which the hydroxyl group-containing copolymerizable vinyl monomer is 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate. It is preferable that it is at least 1 or more types selected from these.

  Moreover, this invention provides the adhesive film characterized by the said adhesive layer being laminated | stacked on the single side | surface of a base material.

  The adhesive film is preferably used for bonding a polarizing plate to a liquid crystal panel or an organic EL panel.

  Further, the present invention is characterized in that the pressure-sensitive adhesive layer is formed with a thickness of 1 μm to 25 μm on one side of the release film, and has a configuration of release film / adhesive layer / release film. An adhesive film is provided.

  The present invention also provides an optical film with an adhesive layer, wherein the adhesive layer is laminated on at least one surface of the optical film.

  Moreover, this invention provides the polarizing plate with an adhesive layer characterized by the said adhesive layer being laminated | stacked on the single side | surface of a polarizing plate.

  In the polarizing plate with the pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer is preferably used for bonding the retardation film having a retardation of λ / 4 or λ / 2 and the polarizing plate.

  Moreover, this invention provides the liquid crystal panel characterized by using the said polarizing plate with an adhesive layer.

  Moreover, this invention provides the on-cell panel characterized by using the said polarizing plate with an adhesive layer.

  According to the present invention, the pressure-sensitive adhesive layer and the pressure-sensitive adhesive film have a low dielectric constant and dielectric loss value as compared with the conventional pressure-sensitive adhesive layer, and have both flexibility, rigidity, durability, and reworkability. Can be provided.

The structure schematic diagram which shows the example of the liquid crystal panel carrying the conventional touch panel. The structure schematic diagram which shows the example of the liquid crystal panel carrying an on-cell type touch panel.

  Hereinafter, the present invention will be described based on preferred embodiments.

  The present invention is an adhesive having both flexibility, rigidity, durability, and reworkability, which is used for bonding optical members in the production of an ITO film-equipped liquid crystal panel called an on-cell panel. An agent layer and an adhesive film are provided.

  FIG. 1 is a structural schematic diagram showing an example of a liquid crystal panel 5 equipped with a conventional touch panel. In such a display device using a liquid crystal panel equipped with a conventional touch panel, a physical space 4 exists between the liquid crystal panel 2 and the touch panel 1. For this reason, external light etc. reflected on the upper surface of the liquid crystal panel 2 and the lower surface of the touch panel 1, and there was a problem that visibility in a bright environment such as outdoors is reduced.

  FIG. 2 is a structural schematic diagram showing an example of a liquid crystal panel 40 equipped with an on-cell touch panel. In the on-cell display device, the touch sensor 10 formed of a transparent electrode pattern is formed between the color filter 13 and the polarizing plate 14, and a touch panel function is provided between the color filter 13 and the polarizing plate 14. The on-cell method has an advantage that the yield of the product is hardly lowered. For this reason, the on-cell method is expected to be developed as a promising manufacturing technology for liquid crystal panels incorporating a touch panel.

In FIG. 2, the pressure-sensitive adhesive layer used for laminating the optical member according to the present invention is a pressure-sensitive adhesive layer having a lower dielectric constant and dielectric loss than the conventional pressure-sensitive adhesive layer. In order to reduce the influence of noise on the capacitive touch panel, it can be used for bonding optical members between the polarizing plate 14 and the backlight unit 30.
The pressure-sensitive adhesive layer according to the present invention is particularly suitably used for bonding the upper and lower polarizing plates 14 and 15 to the liquid crystal panel 20. Specifically, the pressure-sensitive adhesive layer according to the present invention has a polarizing plate 14 and a glass substrate 11 (also referred to as ITO glass) with a touch sensor 10, and a polarizing plate 15 and a TFT electrode 17. In particular, it can be suitably used for bonding to a glass substrate 12 (also referred to as TFT glass).

  The pressure-sensitive adhesive layer of the present invention is a pressure-sensitive adhesive layer formed by crosslinking a pressure-sensitive adhesive composition containing an acrylic polymer and a crosslinking agent, and the acrylic polymer has an alkyl group with a C1-C14 alkyl group. A copolymer obtained by copolymerizing at least one monomer group consisting of a (meth) acrylate monomer, an alicyclic group-containing monomer, and a branched structure alkyl group-containing monomer and a hydroxyl group-containing copolymerizable vinyl monomer. 30 to 100 parts by weight of butyl (meth) acrylate with respect to a total of 100 parts by weight of the monomer excluding the hydroxyl group-containing copolymerizable vinyl monomer, and the hydroxyl group-containing copolymer. 0.1 to 3.5 parts by weight of a functional vinyl monomer, the gel fraction of the pressure-sensitive adhesive layer is 40 to 75%, and the pressure-sensitive adhesive layer is 1000 μm Was measured by laminating a thickness, relative dielectric constant at a frequency of 100kHz is 1.50 to 5.50, and dielectric loss, characterized in that a 0.01 to 0.09.

  The acrylic polymer according to the present invention includes, as monomers belonging to the first monomer group, an alkyl (meth) acrylate monomer having an alkyl group with C1 to C14 carbon atoms, an alicyclic group-containing monomer, a branched structure alkyl group-containing monomer, A monomer group belonging to the first monomer group, a monomer belonging to the second monomer group, and a monomer belonging to the second monomer group, wherein the monomer belonging to the second monomer group is a hydroxyl group-containing copolymerizable vinyl monomer. Are copolymers obtained by copolymerizing one or more of each. In the present specification, (meth) acrylate is a general term for acrylate and methacrylate.

  In the pressure-sensitive adhesive composition according to the present invention, the alkyl (meth) acrylate monomer having an alkyl group with a carbon number of C1 to C14 includes methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) ) Acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate , At least one of tridecyl (meth) acrylate, tetradecyl (meth) acrylate and the like. The alkyl group of the alkyl (meth) acrylate monomer may be linear, branched or cyclic, but here, the alkyl group is linear. The (meth) acrylate monomer having a branched alkyl group belongs to a branched structure alkyl group-containing monomer. Moreover, the (meth) acrylate monomer which has a cyclic alkyl group belongs to an alicyclic group-containing monomer. The acrylic polymer according to the present invention contains butyl (meth) acrylate as an essential monomer. The acrylic polymer preferably contains 30 to 100 parts by weight of butyl (meth) acrylate with respect to a total of 100 parts by weight of monomers (monomers belonging to the first monomer group) excluding the hydroxyl group-containing copolymerizable vinyl monomer. .

  In the pressure-sensitive adhesive composition according to the present invention, as the alicyclic-containing monomer, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, bicycloheptyl (meth) acrylate, bicyclooctyl (meth) acrylate, Examples thereof include at least one of dimethylbicycloheptyl (meth) acrylate and dicyclopentanyl (meth) acrylate. The alicyclic group-containing monomer may be an alicyclic alkyl (meth) acrylate monomer having an alkyl group with C1 to C18 carbon atoms.

  In the pressure-sensitive adhesive composition according to the present invention, the branched alkyl group-containing monomer includes isopropyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, isopentyl (meth) acrylate, and isooctyl (meth) acrylate. , 2-ethylhexyl (meth) acrylate, isononyl (meth) acrylate, isodecyl (meth) acrylate, isoundecyl (meth) acrylate, isododecyl (meth) acrylate, isotridecyl (meth) acrylate, isotetradecyl (meth) acrylate, isopentadecyl (Meth) acrylate, isohexadecyl (meth) acrylate, isoheptadecyl (meth) acrylate, isooctadecyl (meth) acrylate, isomyristyl (meth) a Relate include at least one or more kinds of such isostearyl (meth) acrylate. The branched structure alkyl group-containing monomer may be a branched structure alkyl (meth) acrylate monomer having an alkyl group with C1 to C18 carbon atoms. The branched structure alkyl group-containing monomer may have a branched structure in which the alkyl group has two or more (for example, two or more side chains with respect to the main chain) like a t-butyl group.

  In the pressure-sensitive adhesive composition according to the present invention, examples of the hydroxyl group-containing copolymerizable vinyl monomer include 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 2-hydroxy. Hydroxyl-containing alkyl (meth) acrylates such as ethyl (meth) acrylate, and hydroxyl-containing (meth) acrylamides such as N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, and N-hydroxyethyl (meth) acrylamide And at least one of them. Among them, the compound in which the hydroxyl group-containing copolymerizable vinyl monomer is 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate It is preferably at least one selected from the group. The acrylic polymer according to the present invention contains 0.1 to 0.1 parts of the hydroxyl group-containing copolymerizable vinyl monomer with respect to a total of 100 parts by weight of the monomers excluding the hydroxyl group-containing copolymerizable vinyl monomer (monomers belonging to the first monomer group). Contains 3.5 parts by weight.

  In the pressure-sensitive adhesive composition according to the present invention, the acrylic polymer preferably does not contain a (meth) acrylate monomer having an aromatic group from the viewpoint of lowering the dielectric constant of the pressure-sensitive adhesive layer. Similarly, not only a (meth) acrylate having an aromatic group, but also a copolymerizable vinyl monomer having an aromatic group (such as styrene) may not be contained. Moreover, it is preferable that an acrylic polymer does not contain a carboxyl group-containing copolymerizable vinyl monomer from the viewpoint of avoiding the influence on the corrosiveness of an easily corroded adherend such as the ITO surface of the transparent conductive film. The acid value of the acrylic polymer is preferably 0.1 or less.

  The polymerization method of the copolymer used as the acrylic polymer is not particularly limited, and a known polymerization method such as a solution polymerization method or an emulsion polymerization method can be used as appropriate. The acrylic polymer preferably contains 50 to 100% by weight of an acrylic monomer such as a (meth) acrylate monomer.

  The pressure-sensitive adhesive composition can adjust properties such as required physical property values by blending the acrylic polymer with a crosslinking agent or an appropriate additive as appropriate.

  As the crosslinking agent, for example, a buret modified product of a diisocyanate such as hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, an isocyanurate modified product, trimethylol propane, or a trivalent or higher valent compound such as glycerin. Examples include at least one polyisocyanate compound such as an adduct with a polyol. The acrylic polymer preferably has a hydroxyl group as a functional group capable of undergoing a crosslinking reaction with the isocyanate compound of the crosslinking agent, and preferably contains a monomer having such a functional group in the side chain.

  The content of the isocyanate compound used as the cross-linking agent is 0.01 to 1.5 weights with respect to a total of 100 parts by weight of the monomers (monomers belonging to the first monomer group) excluding the hydroxyl group-containing copolymerizable vinyl monomer. Part is preferred. As the cross-linking agent, only an isocyanate compound may be used. As the isocyanate compound, an adduct of tolylene diisocyanate is preferable, and a trimethylolpropane adduct of tolylene diisocyanate is particularly preferable.

The pressure-sensitive adhesive composition preferably further contains a silane coupling agent. As the silane coupling agent, a compound having at least one organic functional group and at least one hydrolyzable group in one molecule, wherein the hydrolyzable group is an alkoxy group bonded to a silicon atom, or the like. Can be mentioned. It is preferable that the silane coupling agent has at least one organic functional group selected from the group consisting of an epoxy group, a (meth) acryloxy group, a mercapto group, and an amino group. Here, the (meth) acryloxy group means an acryloxy group (CH ₂ ═CHCOO—) or a methacryloxy group (CH ₂ ═C (CH ₃ ) COO—).

Examples of the silane coupling agent having an epoxy group include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and 3-glycidoxypropyl. Triethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethylmethyldimethoxysilane, 2- (3,4-epoxycyclohexyl) ethylmethyldiethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltriethoxysilane, 5,6-epoxyhexyltrimethoxysilane, 5,6-epoxyhexylmethyldimethoxysilane, 5,6-epoxyhexylmethyldiethoxysilane, 5,6- Epoxy hex Such as triethoxy silane.
Examples of the silane coupling agent having a (meth) acryloxy group include 3- (meth) acryloxypropyltrimethoxysilane, 3- (meth) acryloxypropylmethyldimethoxysilane, and 3- (meth) acryloxypropyltriethoxy. Examples thereof include silane, 3- (meth) acryloxypropylmethyldiethoxysilane, 3- (meth) acryloxypropyldimethylethoxysilane, and 3- (meth) acryloxypropyldimethylmethoxysilane.
Examples of the silane coupling agent having a mercapto group include 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldiethoxysilane, and 3-mercaptopropyltriethoxysilane.
Examples of the silane coupling agent having an amino group include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-2- (aminoethyl)- 3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldiethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- (aminoethyl) ) -3-aminopropyltriethoxysilane, 3- (methylamino) propyltrimethoxysilane, 3- (methylamino) propyltriethoxysilane and the like.
Moreover, the oligomerized alkoxy oligomer (silicone alkoxy oligomer) containing the said organic functional group etc. can also be used as a silane coupling agent.

  The content of the silane coupling agent is preferably 0.01 to 2.0 parts by weight with respect to a total of 100 parts by weight of monomers (monomers belonging to the first monomer group) excluding the hydroxyl group-containing copolymerizable vinyl monomer.

  As other optional components, known additives such as an antioxidant, a surfactant, a curing accelerator, a plasticizer, a filler, a crosslinking catalyst, a crosslinking retarder, a curing retarder, a processing aid, and an antiaging agent are appropriately used. Can be blended. These may be used alone or in combination of two or more.

  The pressure-sensitive adhesive layer of the present invention can be obtained by crosslinking the pressure-sensitive adhesive composition after applying the pressure-sensitive adhesive composition to a substrate or a release film. The gel fraction of the adhesive layer after crosslinking is preferably 40 to 75%. Moreover, it is preferable that the weight average molecular weight of an adhesive layer after bridge | crosslinking an adhesive composition is 300,000-2 million. The weight average molecular weight of the pressure-sensitive adhesive layer means an average value through all components contained in the pressure-sensitive adhesive layer, but most of the weight of the pressure-sensitive adhesive layer is an acrylic polymer (crosslinked polymer) crosslinked with a crosslinking agent. And an uncrosslinked acrylic polymer (uncrosslinked polymer). Then, the weight average molecular weight of the pressure-sensitive adhesive layer substantially corresponds to the weight average molecular weight obtained by averaging the crosslinked polymer and the uncrosslinked polymer.

  When used for bonding between layers of optical members, it is desirable that the adhesive layer be a thin adhesive layer. The thickness of the pressure-sensitive adhesive layer is preferably 1 μm to 25 μm, and more preferably 5 μm to 25 μm. In general, the adhesive strength of the pressure-sensitive adhesive layer is substantially proportional to the thickness of the pressure-sensitive adhesive layer, but the adhesive strength of the pressure-sensitive adhesive layer having a thickness of 25 μm is defined as 1. It is preferable that it is 5-10N / 25mm. Examples of the adherend used for the adhesion test include glass plates such as non-alkali glass and resin films.

  When the pressure-sensitive adhesive layer according to the present invention is used for bonding between layers of an optical member, it is desirable that the difference in refractive index is as small as possible in order to reduce the reflection of light rays at the interface between the pressure-sensitive adhesive layer and the optical member. . For this reason, it is preferable that the refractive index of the said adhesive layer is 1.47-1.50.

  When the pressure-sensitive adhesive layer according to the present invention is used in an electronic device such as a touch panel, the relative dielectric constant at a frequency of 100 kHz was measured by laminating the pressure-sensitive adhesive layer to a thickness of 1000 μm from the viewpoint of reducing electromagnetic noise. Is preferably 1.50 to 5.50, and the dielectric loss is preferably 0.01 to 0.09.

The pressure-sensitive adhesive film of the present invention can be produced by forming the pressure-sensitive adhesive layer of the present invention on one side of a substrate or a release film.
As the base film used for forming the pressure-sensitive adhesive layer and the release film (separator) for protecting the pressure-sensitive adhesive surface, a resin film such as a polyester film can be used.
On the base film, on the side opposite to the side where the adhesive layer of the resin film is formed, antifouling treatment with silicone-based, fluorine-based release agent or coating agent, silica fine particles, etc., application of antistatic agent, An antistatic treatment such as kneading can be performed.

The release film is subjected to release treatment with a silicone-based or fluorine-based release agent or the like on the surface of the pressure-sensitive adhesive layer that is to be combined with the pressure-sensitive adhesive surface.
A structure of “release film / adhesive layer / release film” can also be obtained by combining the surfaces of the release layer with the release film subjected to the release treatment. In this case, the release films on both sides can be bonded to an optical member such as an optical film by separating the release films sequentially or simultaneously to expose the adhesive surface. Examples of the optical film include a polarizing film, a retardation film, an antireflection film, an antiglare (antiglare) film, an ultraviolet absorption film, an infrared absorption film, an optical compensation film, and a brightness enhancement film.

The adhesive film of the present invention is applied to various optical films for peripheral members of liquid crystal display devices mainly comprising polarizing plates, various optical films for touch panels, various optical films for electronic paper, various optical films for organic EL, etc. Can be used together.
Moreover, it can be set as the optical film with an adhesive layer by which the said adhesive layer is laminated | stacked on the at least one surface of these optical films. Specifically, “optical film / pressure-sensitive adhesive layer / optical film”, “optical film / pressure-sensitive adhesive layer / release film”, “optical film / pressure-sensitive adhesive layer”, “optical film / pressure-sensitive adhesive layer / optical film / “Adhesive layer / optical film”, “optical film / adhesive layer / optical film / adhesive layer / release film”, “release film / adhesive layer / optical film / adhesive layer / release film”, etc. A configuration is mentioned.
For example, when having a pressure-sensitive adhesive layer protected by a release film such as “optical film / pressure-sensitive adhesive layer / release film”, the release film is peeled off, and “optical film / pressure-sensitive adhesive layer” By exposing the pressure-sensitive adhesive layer and pasting with another optical film, a configuration such as “optical film / pressure-sensitive adhesive layer / optical film” in which the pressure-sensitive adhesive layer is used for bonding between layers is obtained.

  The adhesive film of this invention is used suitably for bonding of a polarizing plate and a display panel. Examples of the display panel include a liquid crystal panel and an organic EL panel. The adhesive film of this invention can be used suitably as an adhesive layer of a polarizing plate with an adhesive layer. As a constituent material of the polarizing plate, a retardation film having a retardation of λ / 4 or λ / 2 may be used. The pressure-sensitive adhesive layer of the present invention can be used for bonding the retardation film and the polarizing plate. According to the pressure-sensitive adhesive film of the present invention, since the pressure-sensitive adhesive layer has a low dielectric constant, in an on-cell display device in which a touch sensor is provided between the color filter and the polarizing plate, between the polarizing plate and the backlight unit. It can be suitably used for bonding optical members.

  Hereinafter, the present invention will be specifically described with reference to examples.

<Manufacture of acrylic polymer>
[Example 1]
Nitrogen gas was introduced into a reactor equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, and the air in the reactor was replaced with nitrogen gas. Thereafter, 100 parts by weight of butyl acrylate and 0.2 parts by weight of 8-hydroxyoctyl acrylate as well as 60 parts by weight of a solvent (ethyl acetate) were added to the reactor. Thereafter, 0.1 part by weight of azobisisobutyronitrile as a polymerization initiator was dropped over 2 hours and reacted at 65 ° C. for 6 hours to obtain an acrylic polymer solution 1 used in Example 1. A part of the acrylic polymer was collected and used as an acid value measurement sample described later.
[Examples 2 to 4 and Comparative Examples 1 to 3]
Examples 2 to 4 and Examples 2 and 4 were carried out in the same manner as in the acrylic polymer solution 1 used in Example 1 except that the monomer compositions were as described in groups (1) and (2) in Table 1. An acrylic polymer solution used in Comparative Examples 1 to 3 was obtained.

<Manufacture of an adhesive composition, an adhesive layer, and an adhesive film>
[Example 1]
0.2 parts by weight of coronate L (75% ethyl acetate solution of trimethylolpropane (TMP) adduct of tolylene diisocyanate (TDI) compound) with respect to acrylic polymer solution 1 of Example 1 produced as described above, 0.05 parts by weight of KBM-403 (3-glycidoxypropyltrimethoxysilane) was added and mixed by stirring to obtain a pressure-sensitive adhesive composition of Example 1. After applying this pressure-sensitive adhesive composition onto a release film (polyethylene terephthalate (PET) film coated with a silicone resin), the solvent was removed by drying at 90 ° C., and an atmosphere at 23 ° C. and 50% RH. A pressure-sensitive adhesive film of Example 1 having a pressure-sensitive adhesive layer having a thickness of 25 μm formed by crosslinking the pressure-sensitive adhesive composition on one surface of the release film was obtained by aging for 7 days.
[Examples 2 to 4 and Comparative Examples 1 to 3]
Examples 2 to 4 and Comparative Example 1 were carried out in the same manner as the adhesive film of Example 1 except that the compositions of the additives were as described in the groups (3) and (4) of Table 1. -3 adhesive films were obtained.

In Table 1, the total of the monomer group which consists of the alkyl (meth) acrylate monomer whose carbon number of an alkyl group is C1-C14, an alicyclic group containing monomer, and a branched structure alkyl group containing monomer of (1) group, It calculated | required as 100 weight part. Moreover, the numerical value of a weight part is shown enclosed with a parenthesis as an addition ratio from (2) group to (4) group. However, in Example 2, the total of group (1) was 90 parts by weight. In the case of Comparative Examples 1 and 2, the group (1) further includes a (meth) acrylate monomer having an aromatic group.
Group (2) is a hydroxyl group-containing copolymerizable vinyl monomer, but in Comparative Examples 1 and 3, it is a monomer group consisting of a hydroxyl group-containing copolymerizable vinyl monomer and a carboxyl group-containing copolymerizable vinyl monomer. is there. (3) Group is a crosslinking agent. (4) Group is a silane coupling agent.

  In addition, Table 2 shows the names of the abbreviations of each component used in Table 1. Coronate (registered trademark) L is a trade name of Nippon Polyurethane Industry Co., Ltd., D-110N is a trade name of Mitsui Chemicals, Inc., and KBM-403 and KBM-803 are trade names of Shin-Etsu Chemical Co., Ltd. It is. TDI means tolylene diisocyanate, TMP means trimethylolpropane, and XDI means xylylene diisocyanate.

<Test method and evaluation>
From the adhesive films in Examples 1 to 4 and Comparative Examples 1 to 3, the release film (silicone resin-coated PET film) was peeled off to expose the adhesive layer, and the adhesive on one side of the polarizing plate (film) The layer was transferred.

<Measurement method of adhesive strength>
A pressure-sensitive adhesive layer having a thickness of 25 μm was transferred to one surface of a polarizing plate (film) having a thickness of 180 μm to obtain a pressure-sensitive adhesive film (optical film with a pressure-sensitive adhesive layer) as a sample.
The obtained adhesive film was bonded to a non-tin surface washed with non-alkali glass acetone with a pressure roll and autoclaved under conditions of 50 ° C. and 0.5 MPa × 20 minutes, and then an atmosphere of 23 ° C. × 50% RH. Returned to 1 hour. The peel strength of the subsequent adhesive film was measured with a tensile tester in accordance with JIS Z0237 “Test method for adhesive tape / adhesive sheet”, and the peel strength when peeled at a rate of 300 mm / min in the 180 ° direction was It was set as the adhesive force (N / 25mm) of the adhesive layer of an adhesive film.

<Method for measuring acid value>
The acid value of the acrylic polymer was determined by dissolving the sample in a solvent (diethyl ether and ethanol mixed at a volume ratio of 2: 1) and using an automatic potentiometric titrator (AT-610, manufactured by Kyoto Electronics Industry). 1 Using the above potentiometric titrator, potentiometric titration was performed with a potassium hydroxide ethanol solution having a concentration of about 0.1 mol / l, and the amount of potassium hydroxide ethanol solution necessary to neutralize the sample was measured. And the acid value was calculated | required from the following formula.
Acid value = (B × f × 5.611) / S
B = Amount of 0.1 mol / l potassium hydroxide ethanol solution used for titration (ml)
f = factor of 0.1 mol / l potassium hydroxide ethanol solution S = mass (g) of solid content of sample

<Method for measuring gel fraction>
After the aging is completed, the mass of the measurement sample before being bonded to the polarizing plate is accurately measured, immersed in toluene for 24 hours, and then filtered through a 200 mesh wire net. Then, after drying a filtered material at 100 degreeC for 1 hour, the mass of the residue was measured correctly and the gel fraction of the adhesive layer (adhesive after bridge | crosslinking) was computed from the following formula | equation.
Gel fraction (%) = insoluble partial mass (g) / adhesive mass (g) × 100

<Durability test method>
A sample prepared by laminating a 10 cm square adhesive film prepared by the same method as the measurement of adhesive strength on the non-tin surface of non-alkali glass by the same method was used in a predetermined atmosphere (80 ° C. dry atmosphere or 60 ° C. In an atmosphere of 90% RH for 250 hours, it was taken out in an atmosphere of 23 ° C. and 50% RH, and after 1 hour, the state of the adhesive film was visually observed to determine durability.
○ ・ ・ There is no peeling or foaming of the adhesive film.
Δ ·· Peeling and foaming occurred on part of the adhesive film.
× ·· Peeling and foaming occurred on the entire adhesive film.

<Measurement method of relative permittivity and dielectric loss>
A pressure-sensitive adhesive layer having a thickness of 1000 μm was used as a measurement sample. Using an LCR meter, the measurement sample was sandwiched between jigs of the LCR meter, and the relative dielectric constant and dielectric loss were measured at a frequency of 100 to 200 kHz.

<On-cell panel response>
After sticking a polarizing plate on which an adhesive layer with a thickness of 20 μm is layered on an on-cell panel (TOD, Touch On Display), the touch operation is performed from the surface of the polarizing plate, and the touch operation location is changed. The response reactivity was examined and evaluated according to the following criteria.
○ ·· Good response reactivity.
× ·· Poor response.

<Test method for reworkability>
A sample prepared by laminating a 10 cm square adhesive film prepared by the same method as the measurement of adhesive strength on the non-tin surface of non-alkali glass by the same method was left in an atmosphere of 70 ° C. for 10 days, and then 23 The reworkability was judged by measuring the adhesive strength of the adhesive film after taking it out in an atmosphere at 0 ° C. and leaving it for 1 hour.
○ ·· Adhesive strength after 10 days at 70 ° C. is 1.5 to 10 N / 25 mm.
Δ ·· 70 ° C. × 10 days later, the adhesive strength is greater than 10 N / 25 mm, but 20 N / 25 mm or less.
× · The adhesive strength after 70 ° C. × 10 days is greater than 20 N / 25 mm (cannot be removed).

  Tables 3 and 4 show the evaluation results.

  The adhesive films of Examples 1 to 4, which are the adhesive films according to the present invention, have an adhesive strength of 1.5 to 10 N / 25 mm after an adhesive layer having a thickness of 25 μm is allowed to pass for 23 ° C. × 10 days. The gel fraction of the pressure-sensitive adhesive layer after crosslinking is 40 to 75%, the weight average molecular weight of the pressure-sensitive adhesive layer after crosslinking is 300,000 to 2,000,000, and the acid value of the acrylic polymer is 0.1 or less. Yes, adhesion and durability were excellent. Moreover, after bonding the adhesive film of Examples 1-4 to a to-be-adhered body, it is excellent also in rework property because the adhesive force after 70 degreeC x 10 days is the range of 1.5-10N / 25mm. It was. That is, according to the adhesive films of Examples 1 to 4, the requirements and problems in the prior art could be overcome.

  The pressure-sensitive adhesive film of Comparative Example 1 includes an acrylic polymer-containing monomer that does not contain butyl acrylate, includes a (meth) acrylate monomer having an aromatic group, and a carboxyl group-containing copolymerizable vinyl monomer, and the gel fraction of the pressure-sensitive adhesive layer , The weight average molecular weight of the pressure-sensitive adhesive layer after crosslinking was small, and the acid value of the acrylic polymer was high. Because of these influences, when the thickness of the pressure-sensitive adhesive layer is 25 μm, the adhesive strength of the pressure-sensitive adhesive layer is strong, the durability at 80 ° C. dry is slightly inferior, and durability under an atmosphere of 60 ° C. × 90% RH It was inferior to reworkability. Moreover, the relative dielectric constant and dielectric loss were high, and the on-cell panel response was poor.

  The pressure-sensitive adhesive film of Comparative Example 2 includes a (meth) acrylate monomer having an acrylic polymer as a constituent monomer of an acrylic polymer, a large content of a hydroxyl group-containing copolymerizable vinyl monomer, a large amount of a crosslinking agent, and a gel The percentage was high. Because of these influences, when the thickness of the pressure-sensitive adhesive layer is 25 μm, the adhesive strength of the pressure-sensitive adhesive layer is strong, the durability under an atmosphere of 60 ° C. × 90% RH is poor, and the reworkability is slightly inferior. . Further, the dielectric loss was high and the on-cell panel response was poor.

  Since the adhesive film of Comparative Example 3 did not contain a crosslinking agent, the acrylic polymer was not crosslinked, the gel fraction was 0, and the weight average molecular weight of the adhesive layer after crosslinking was small. The acrylic polymer contains a carboxyl group-containing copolymerizable vinyl monomer and has a high acid value. Because of these influences, when the thickness of the pressure-sensitive adhesive layer was 25 μm, the pressure-sensitive adhesive force of the pressure-sensitive adhesive layer was very strong and inferior in durability and reworkability. Moreover, the relative dielectric constant was high, and the on-cell panel response was poor.

  As described above, the pressure-sensitive adhesive films of Comparative Examples 1 to 3 could not overcome the requirements and problems in the prior art.

DESCRIPTION OF SYMBOLS 1 ... Touch panel, 2 ... Liquid crystal panel, 3 ... Backlight unit, 4 ... Space, 5 ... Liquid crystal panel equipped with the touch panel, 10 ... Touch sensor, 11, 12 ... Glass substrate, 13 ... Color filter, 14, 15 ... Polarization Plate: 16 ... Transparent electrode, 17 ... TFT electrode, 18 ... Liquid crystal layer, 20 ... Liquid crystal panel, 30 ... Backlight unit, 40 ... Liquid crystal panel equipped with an on-cell touch panel.

Claims (9)

It is a pressure-sensitive adhesive layer formed by crosslinking a pressure-sensitive adhesive composition containing an acrylic polymer, a crosslinking agent, and a silane coupling agent.
The acrylic polymer is
(A) a total of 100 parts by weight of at least one monomer group consisting of an alkyl (meth) acrylate monomer having a C1-C14 alkyl group, an alicyclic group-containing monomer, and a branched structure alkyl group-containing monomer; ,
(B) a copolymer obtained by copolymerizing 0.1 to 3.5 parts by weight of a hydroxyl group-containing copolymerizable vinyl monomer,
A total of 100 parts by weight of the (A) contains butyl (meth) acrylate in a proportion of 30 to 60 parts by weight,
The (B) hydroxyl group-containing copolymerizable vinyl monomer is composed of 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 2-hydroxyethyl (meth) acrylate. At least one selected from the group of compounds consisting of:
The acrylic polymer does not contain a (meth) acrylate monomer having an aromatic group and a carboxyl group-containing copolymerizable vinyl monomer,
The acid value of the acrylic polymer is 0.1 or less,
100 parts by weight of the total of the (A), as the crosslinking agent, and 0.01 to 1.5 parts by weight of an isocyanate compound only a trimethylolpropane adduct of tolylene diisocyanate, as the silane coupling agent , Containing at least one silane coupling agent having an organic functional group selected from the group consisting of an epoxy group, a (meth) acryloxy group, a mercapto group, and an amino group in a proportion of 0.01 to 2.0 parts by weight And
The gel fraction of the pressure-sensitive adhesive layer is Ri 40-75% der,
The pressure-sensitive adhesive layer was measured by laminating to a thickness of 1000 .mu.m, a relative dielectric constant at a frequency of 100kHz is 1.50 to 5.50, and dielectric loss of 0.01 to 0.09 der Rukoto Characteristic pressure-sensitive adhesive layer.   A pressure-sensitive adhesive film, wherein the pressure-sensitive adhesive layer according to claim 1 is laminated on one side of a substrate.   The pressure-sensitive adhesive film according to claim 2, wherein the pressure-sensitive adhesive film is used for bonding a polarizing plate to a liquid crystal panel or an organic EL panel.   The pressure-sensitive adhesive layer according to claim 1 is formed with a thickness of 1 μm to 25 μm on one side of the release film, and has a structure of release film / adhesive layer / release film. the film.   An optical film with an adhesive layer, wherein the adhesive layer according to claim 1 is laminated on at least one surface of the optical film.   The polarizing plate with an adhesive layer, wherein the adhesive layer according to claim 1 is laminated on one side of the polarizing plate.   The pressure-sensitive adhesive layer is used for laminating a retardation film having a phase difference of λ / 4 or λ / 2 and the polarizing plate. Polarizer.   A liquid crystal panel using the polarizing plate with an adhesive layer according to claim 6.   An on-cell panel, wherein the polarizing plate with the pressure-sensitive adhesive layer according to claim 6 is used.

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